When viewing a vehicle you'll see 'Appointments' in the left sidebar, the vehicle must have been published For Sale for this option to be available.
This section allows you to manually add appointments which are related to this vehicle. Simply click 'Add Appointment' and you'll be able to choose between an appointment and a reminder with the first checkbox. On that same top line you can choose which of your calendars you wish to make the booking in. There is a shortcut to manage your calendars at the top, should you wish to colour-code them or add new calendars.
Select the date, time and duration of your appointment. There is also an option to set a reminder to follow up to the meeting.
You can connect the appointment to a customer by starting to type their name into the search box. If it's a new customer you can click 'New Contact'. You can then add as many members of staff/users as you like into the appointment under 'Staff/Users'.
Type the subject of/reason for the meeting into 'Purpose' and tag any vehicles that need to be discussed by typing their registration into the 'Vehicles Of Interest' textbox.
Finally, you can add any notes to the appointment. These are internal notes and will not be shared with the customer.
Once you're happy with all the details, click 'Add Appointment' and you'll see it in the calendar you selected.